### Spring 2008 Physics 101 Hour Exam 1(25 questions)

The grading button and a description of the scoring criteria are at the bottom of this page. Basic questions are marked by a single star *. More difficult questions are marked by two stars **. The most challenging questions are marked by three stars ***.

True-false questions are worth 2 points each, three-choice multiple choice questions are worth 3 points each, five-choice multiple choice questions are worth 6 points each. The maximum possible score is 102. The exam period was 90 minutes; the mean score was 74.7; the median score was 77. Click here to see page1 page2 of the formula sheet that came with the exam.

### QUESTION 1*

This and the following question concern the same physical situation.

Fred, whose mass is 60 kg, is riding on an elevator. He feels as if he weighs 612 N. How fast is the elevator accelerating?

(a)   0.18 m/s2
(b)   0.26 m/s2
(c)   0.4 m/s2

### QUESTION 2**

The elevator is traveling

(a)   upward.
(b)   downward.
(c)   not enough information

### QUESTION 3*

This and the following question concern the same physical situation.

Sally drops a bowling ball from a rooftop of height 65 m. How long does it take the ball to reach the ground? (Neglect air resistance.)

(a)   3.64 s
(b)   4.12 s
(c)   5.86 s
(d)   6.77 s
(e)   7.87 s

### QUESTION 4*

What is the speed of the ball when it reaches the ground?

(a)   18.2 m/s
(b)   21.3 m/s
(c)   28.6 m/s
(d)   35.7 m/s
(e)   41.2 m/s

### QUESTION 5*

This and the following two questions concern the same physical situation.

Harvey is riding on a raft that floats in a river. The river and raft move together southward at a speed of 3 mph. Harvey walks due west, with respect to the raft, at a speed of 2 mph.

Harvey's net speed with respect to the ground is

(a)   2.8 mph
(b)   3.2 mph
(c)   3.6 mph
(d)   4.5 mph
(e)   5.1 mph

### QUESTION 6*

If Harvey walked instead due north, at the same speed, his speed with respect to the ground would be

(a)   5 mph
(b)   1 mph
(c)   0 mph

### QUESTION 7*

This and the following two questions concern the same physical situation.

A baseball player throws a ball at an initial speed of 12 m/s at an angle of 30° above the horizontal (neglect air resistance, and assume the ball starts at the same height as the ground).

How long does the ball stay in the air?

(a)   0.228 s
(b)   0.626 s
(c)   0.801 s
(d)   1.22 s
(e)   1.76 s

### QUESTION 8*

How far does the ball travel before hitting the ground?

(a)   5.46 m
(b)   5.58 m
(c)   10.49 m
(d)   12.81 m
(e)   12.73 m

### QUESTION 9**

If the ball were thrown at double the speed (24 m/s) the horizontal distance it would travel would be

(a)   unchanged.
(b)   twice as large.
(c)   four times as large.

### QUESTION 10*

This and the following two questions concern the same physical situation.

A box slides down a frictionless, inclined plane that makes an angle with the horizontal. Let the symbol F denote the component of the force parallel to the ramp, m the mass of the box, and N the normal force.

Which one of the following statements is true?

(a)   F = mg cos(θ) and N = mg sin(θ)
(b)   F = mg tan(θ) and N = mg sin(θ)
(c)   F = mg sin(θ) and N = mg cos(θ)
(d)   F = mg sin(θ) and N = mg
(e)   F = mg and N = mg sin(θ)

### QUESTION 11*

What is the magnitude of the net force acting on the box?

(a)   mg cos(θ)
(b)   mg sin(θ)
(c)   mg

### QUESTION 12**

If the mass of the box doubles its acceleration down the ramp

(a)   doubles.
(b)   halves.
(c)   remains the same.

### QUESTION 13*

This and the following two questions concern the same physical situation.

You are traveling in an airplane at 500 miles/hour due east. There is a strong crosswind blowing from north to south, at 200 miles/hour. The airplane has mass 104 kg.

What is the total distance traveled by the airplane in 1 hour?

(a)   500 miles
(b)   539 miles
(c)   700 miles

### QUESTION 14**

The airplane enters a region with strong turbulence. As a consequence, there is no net force acting between the plane and the air for 2 seconds. What happens to the airplane during this time?

(a)   The airplane stays at the same altitude.
(b)   The airplane drops 9.8 m.
(c)   The airplane drops 19.6 m.

### QUESTION 15*

At the instant the airplane begins to drop, a passenger is standing in the aisle. What happens to this passenger?

(a)   She accelerates upward compared to the airplane and hits the ceiling.
(b)   She feels weightless while the airplane is dropping.
(c)   She feels a force pushing her towards the floor.

### QUESTION 16**

This and the following question concern the same physical situation.

A skier is initially at rest on a ski slope as shown. The coefficient of static friction between the skis and the slope is 0.1. The coefficient of kinetic friction is 0.05.

What is the smallest angle θ such that the skier will start to move without pushing off?

(a)   5.71°
(b)   7.10°
(c)   8.49°
(d)   9.83°
(e)   11.21°

### QUESTION 17**

Once the skier is moving, what will be his net acceleration?

(a)   0.25 m/s2
(b)   0.49 m/s2
(c)   0.98 m/s2

### QUESTION 18***

This and the following question concern the same physical situation.

An acrobat is hanging off of two ropes, one vertical and one at an angle θ of 45°. The acrobat's mass is 70 kg.

What is the tension in the angled rope?

(a)   0 N
(b)   485 N
(c)   686 N

### QUESTION 19***

The acrobat lets go of the vertical rope while holding on to the angled rope. What is the tension in the angled rope the instant after letting go?

(a)   0
(b)   485 N
(c)   686 N

### QUESTION 20**

A locomotive pulls a train of 20 rail cars, accelerating it at 1 m/s2. You place a force probe between the 10th and the 11th car and you find that the force between them is 10000N. What is the mass of one of the cars?

(a)   500 kg
(b)   1000 kg
(c)   10000 kg
(d)   11000 kg
(e)   20000 kg

### QUESTION 21**

You and a friend find yourselves standing on extremely slippery ice at the centre of circular frozen lake without any equipment. The shore is 100 m away. Assume that there is no friction between you and the ice and that it is too cold to even consider removing any of your clothes, or to melt the ice. Also, you and your fried have exactly the same mass. Which of the following statements is true?

(a)   It is impossible for both of us to reach the shore.
(b)   I can reach the shore before my friend.
(c)   It is possible for only one of us to reach the shore with the other remaining on the ice.
(d)   Either both of us or none of us can reach the shore.
(e)   None of the above.

### QUESTION 22**

This and the following question concern the same physical situation.

A cannonball is shot at an upward angle of 45° from horizontal. As it exits the cannon, the ball has speed of 100 m/s. The mass of the cannon ball is 10 kg. You may assume that the muzzle exit of the cannon is at the same height as the target.

The cannon ball hits the target exactly. How far is the target from the cannon?

(a)   510 m
(b)   1020 m
(c)   1883 m

### QUESTION 23**

Assume the cannon ball is shot exactly due north. A wind blows from west to east which exerts a constant net force of 3 N on the cannon ball throughout its flight. By what distance does the ball miss the target?

(a)   15.6 m
(b)   31.2 m
(c)   62.4 m

### QUESTION 24**

From one birthday to the next you travel around the sun once, ending up exactly where you started one year before. What are the x and y components of your average velocity on your yearly journey around the sun? Assume that your average speed is 30 km/s. Assume also that the sun itself is not moving.

(a)   vx = 0 m/s, vy = 0 m/s
(b)   vx = 30000 m/s, vy = 0 m/s
(c)   vx = 30000 m/s, vy = 30000 m/s

### QUESTION 25***

During the shooting of a movie, an actor is attached to a taught cable making an angle θ with the vertical direction. What is the acceleration of the actor the moment his support is removed?

(a)   0 m/s2
(b)   sin(θ) g
(c)   cos(θ) g

Scoring of True-False (T,F) Questions:
• If you mark the correct answer, you get 2 points.
• If you mark the wrong answer or if you mark neither answer, you get 0 points.
Scoring of Multiple Choice I (a,b,c) Questions:
• If you mark the correct answer, you get 3 points.
• If you mark a wrong answer or if you mark none of the answers, you get 0 points.
Scoring of Multiple Choice II (a,b,c,d,e) Questions:
• If you mark one answer and it is the correct answer, you get 6 points.
• If you mark two answers and one of them is the correct answer, you get 3 points.
• If you mark three answers and one of them is the correct answer, you get 2 points.
• If you do not mark the correct answer, or if you mark more than three answers, or if you mark none of the answers, you get 0 points.